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Amorphous and crystalline SiC nanoparticles were synthesized via laser ablation of SiC micro-sized powder in water and ethanol. X-ray and HRTM analysis showed the amorphous nature of SiC nanoparticles with an average particle size of 44 nm in water and crystalline 6H-SiC polytype nanoparticles with an average size of 18 nm in ethanol. The direct and indirect bandgap of SiC nanoparticles were determined from UV–visible absorption spectra. PL emission characteristics were studied and crystalline SiC nanoparticles exhibit tunable PL emission covering UV to the visible region.

The commercial viability of fuel cells for vehicle application has been examined in the context of lightweight material options, as well as in combination with improvements in fuel cell powertrain. Investigation into ultra-lightweight bipolar plates (BPs), the main component in terms of the weight effect, is of great importance to enhance energy efficiency. This research aims to fabricate a layered carbon fiber/epoxy composite structure for BPs. Two types of carbon fillers (COOH-MWCNT and COOH-GNP) reinforced with woven carbon fiber sheets (WCFS) have been utilized. The conceptual idea is to reduce molding cycle time by improving the structural, electrical, and mechanical properties of BPs. Reducing the reactive molding cycle time is required for commercial production possibility. The desired crosslink density of 97%, observed at reactive molding time, was reduced by 83% at 140 °C processing temperature. The as-fabricated BPs demonstrate excellent electrical conductivity and mechanical strength that achieved the DOE standard. Under actual fuel cell operation, the as-fabricated BPs show superior performance to commercial furan-based composite BPs in terms of the cell potential and maximum power. This research demonstrates the practical and straightforward way to produce high-performance and reliable BPs with a rapid production rate for actual PEMFC utilization.

Pulsed laser ablation in liquid technique (PLAL) had started getting attention in late 1990, particularly for the production of the nanomaterials due to its easy handling and room-temperature synthesis process. Soon after the initial demonstration of nanomaterials generation from the PLAL technique, PLAL gradually becomes a green, facile and inexpensive method for the generation of ultrapure carbon nanomaterials (CNMs). In the past two decades, different allotropic forms of CNMs have been fabricated by using PLAL techniques such as graphene/graphene oxide nanosheet, carbon nanotubes, graphene oxide quantum dots, nanodiamonds, carbogenic nanoparticles, polyynes and carbon-encapsulated metal-based nanoparticles. In this review article, we offer a comprehensive discussion on the progress achieved in the design and development of the PLAL method for the production of CNMs only (the year 1998–2020). Firstly, we have introduced the different types of PLAL methods widely used for CNMs fabrication. Secondly, the different types of factors affecting the physicochemical (structural, morphological, optical) properties of CNMs and the efficiency of CNMs production from PLAL method have been summarized in detail. The laser parameters and experimental conditions of the PLAL method, that affecting the physicochemical properties and efficiency of CNMs production are laser wavelengths, pulse duration and repetition rate, ablation duration, per-pulse energy density (fluence), PLAL setup design and nature of solvents. The results from different spectroscopic techniques for each kind of CNMs have been discussed thoroughly, to unambiguously differentiate the structural integrity of the CNMs from one another. Finally, the uses of CNMs for different applications in the present time, existing challenges in the PLAL methods and the future outlook of laser-assisted synthesized CNMs for novel applications were also discussed.

In this work, we report a template-free synthesis of graphene oxide nanosphere (GONs) by the laser ablation of graphene in ethanol. The GONs were formed by crumpling of graphene sheet under the infrared nanosecond pulsed laser irradiation. FESEM and HRTEM images of as-prepared GONs were recorded to analyse the morphological characteristics. Raman, X-ray photoelectron and FTIR spectroscopy results confirmed the formation of GONs under the laser ablation. GONs exhibited the particle size ranges from 100 nm to 700 nm and the average particle size was estimated to be around 137 nm by particle size analyser. Photoluminescence study revealed bright blue-green PL emission under the excitation wavelength of 320–420 nm for GONs.

Multi-walled carbon nanotubes (MWCNTs) were decorated with palladium nanoparticles (Pd NPs) by laser-ablation of a physical mixture of MWCNTs and Pd NPs without using any reducing agent. The morphology and composition of MWCNT/Pd were analysed by complementary techniques involving Fourier transform infrared spectrometry, transmission electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. Using cyclic voltammetry and chronoamperometry, the electrocatalytic activity and stability of CNT/Pd were evaluated for the electrochemical oxidation of methanol in a basic medium. Comparative investigations were provided with laser-ablated Pd NPs (LA Pd) catalyst concerning catalytic activity and stability. MWCNT/Pd exhibited remarkably high catalytic activity (104.20 mA mg−1) in comparison to the LA Pd catalyst (14.41 mA mg−1). The catalyst was found to exhibit long-term stability even after 3600 s of operation and high resistance towards CO poisoning. It is suggested that the MWCNT/Pd would be valuable as an active electrocatalyst for its commercial applications in direct methanol fuel cells.

In this report, silver nanoparticles (Ag-NPs) were prepared by pulsed laser ablation of the silver nitrate salt solution using Nd:YAG laser. Trisodium citrate (TSC) is used as a stabilizing/reducing agent for nanoparticles. Under different laser ablation durations, the morphology of nanoparticles changed. Nanoparticles showed the average size ranging from 5 to 31 nm for 20–80 min of ablation. The theoretical and experimental estimation of the particle sizes is done. Butterfly-shaped silver nanoparticles have been tested for the room-temperature clad-modified fiber optic gas sensors sensitivity with ammonia and ethanol gas. The clad-modified optical fiber sensor exhibits distinct linear variation in the spectral peak intensity with the ammonia concentration (0–500 ppm). The characteristics of the gas sensors when exposed to ethanol and ammonia gases were used for studying the sensor selectivity. The results exhibited good sensor response and selectivity for ammonia with sensitivity of 64 counts/ppm and sensitivity percentage of 27%, whereas for ethanol, sensitivity of 9.5 counts/ppm and sensitivity percentage of only 4% were observed.

In this work, a simple nonenzymatic glucose sensor has been proposed based on coconut shell charcoal (CSC) modified nickel foil as working electrode in a three-electrode electrochemical cell. Charcoal was prepared by the pyrolysis of coconut shells. The most important advantages of coconut shells are cost-effectiveness and their abundance in nature. The morphology and phase of the CSC powder were characterized by scanning electron microscopy and X-ray diffraction. The electrochemical performance of the CSC powder coated Nickel foil electrode was investigated by cyclic voltammetry and chronoamperometry. The sensor shows a higher sensitivity of 2.992 mA cm−2 mM−1 in the linear range of 0.5–5.5 mM and slightly lower sensitivity of 1.1526 mA cm−2 mM−1 in the range of 7–18.5 mM glucose concentration with a detection limit of 0.2 mM. The anti-interference property of CSC powder also was investigated and found that the response of interfering species was less significant compared to glucose response. The proposed sensor offers good sensitivity, wide linear range, and a very low response to interfering biomolecules.

Carbon nanoparticles (CNPs) were prepared by laser ablation of activated carbon (4% ash) in water + ethanol solution (5:2 by volume). Average particle size of about 14 nm was observed and CNPs exhibited a crystalline structure. When 2 mL of NaOH (0.185 M) was added to water + ethanol solution, the average particle size was about 4 nm and the amorphous structure was observed. Photoluminescence (PL) of synthesized CNPs in the absence of NaOH showed spectral peak intensity in the blue region (466 nm) whereas it shifted to the green region (515 nm) for CNPs synthesized with NaOH. The PL of both CNPs exhibited excitation dependent. FWHM of PL spectra of CNPs decreased with increase in the excitation wavelength for a solution without NaOH whereas it increased initially and then decreased for CNPs synthesized with NaOH.

The present study employed laser ablation to obtain fluorescent carbon nanoparticles (CNPs) using inexpensive and easily available Bougainvillea alba flower juice extract as the source. The laser ablation of flower juice extract was carried out using 355 nm wavelength of Nd: YAG pulsed laser for 60 min. HR-TEM studies showed the presence of both larger (about 60 nm) and smaller size (about 10 nm) CNPs and average particle size was found to be about 25 nm. Crystalline structure was also observed in CNPs, whose interplanar lattice spacing was 0.27 nm, indicating the contracted lattice spacing from usual graphitic structure. XRD and Raman analysis showed that the crystalline CNPs correspond to non-perfect graphitic carbon structure. Optical spectroscopic studies revealed the down-conversion of photoluminescence emission at 485 nm under the excitation wavelength of 400 nm. The average fluorescence lifetime of carbon nanoparticles was estimated as 1.1 ns from time-resolved spectroscopy. The CNPs were found to be non-toxic to human vein endothelial cells and internalized into the cells with high intensity up to 24 h. Two distinct PL emissions were observed with the large particles emitting at the longer wavelength localized predominantly in the cytosol and smaller particles emitting at the shorter wavelength concentrated on the nuclear membrane. The results suggest that the CNPs are biocompatible and have the potential for bioimaging applications.

Traditionally, CNPs directly obtained from nanosecond pulsed laser ablation (ns-PLA) in an organic solvent like ethanol, isopropyl alcohol and acetone, possess toxic characteristics with excellent fluorescent properties. However, water-soluble CNPs are found to be non-toxic with weak fluorescent properties. In this study, a post-ablation method was utilized to achieve water-soluble fluorescent CNPs. Initially, the colloidal Eth-CNPs solution was obtained from ns-PLA of charcoal powder in the ethanol, which was subsequently dried at room temperature and then dispersed in water to achieve the final water-soluble CNPs (W-CNPs). The High-resolution Transmission Electron Microscopy (HRTEM) image analysis of W-CNPs shows quasi-spherical size particle distribution with an average particle size found to be around 21 nm. XPS studies of charcoal powder and W-CNPs confirm the creation of fluorescent emissive defects state on the surface of W-CNPs under laser ablation in ethanol. Photoluminescence studies of W-CNPs demonstrated the wavelength-dependent PL emission, with peak PL emission in the blue region of the visible spectrum. In vitro studies indicated the non-toxic nature of the W-CNPs at low and high concentration (1, 5 and 10% v/v) in human cardiomyocytes. Herein, the W-CNPs obtained from post-ns-PLA was found to exhibit both blue and green fluorescence in the cardiomyocytes and hence, it can be exploited as a fluoro probe in bioimaging applications.

Graphene oxide nanoparticles (nGOs) were prepared by nanoscond pulsed laser ablation (ns-PLA) of graphene solution at a wavelength of 1064 nm. The High-Resolution Transmission Electron Microscopy (HR-TEM) reveals the average particles size of nGOs as 26 nm with an interplanar spacing of 0.21–0.24 nm indicating the crystalline nature of nGOs. X-ray Diffraction (XRD) analysis exhibited peak at 14.4° suggesting the exfoliation of graphene sheet under the PLA of graphene solution. Raman, Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Photoelectron Spectroscopic (XPS) analysis reveals the oxidation of graphene precursor. Photoluminescence (PL) studies of nGOs showed the excitation-dependent PL emission with peak PL emission intensity in the bluish-green region (455 nm). In-vitro studies indicate that synthesized nGOs at a low and high concentration (1, 5 and 10% v/v) showed no direct cytotoxicity on smooth muscle cells at different time points. Moreover, they do not affect the proliferation rate of smooth muscles cells. Herein, nGOs prepared by PLA was found to be photoluminescent and biocompatible, which can be utilized for bioimaging applications.